As a technique which is of interest to the present invention, Japanese Unexamined Patent Application Publication No. 2005-15654 (Patent Document 1) describes a technique regarding a binder resin for a conductive paste having excellent heat decomposability and adhesiveness to ceramic green sheets, and a conductive paste which does not cause cobwebbing and clogging and has an excellent printing property. More specifically, it describes a binder resin for a conductive paste, which contains a polyvinyl acetal(meth)acrylate composite resin obtained by adding a polymerizable monomer mainly composed of a (meth)acrylate to an aqueous medium in which a polyvinyl acetal resin is dispersed and causing the polymerizable monomer to permeate into the polyvinyl acetal resin, followed by polymerization, and a conductive paste which includes the binder resin for a conductive paste and a metal material.
On the other hand, Japanese Unexamined Patent Application Publication No. 2006-210256 (Patent Document 2) describes a vehicle for a coating paste, which has excellent adhesiveness, which is capable of preventing the occurrence of delamination, and which has an excellent coating property and screen printing property, and a coating paste including the same. More specifically, it describes a vehicle for a coating paste containing a modified polyvinyl acetal resin having structural units represented by specific general formulae and an organic solvent, in which the modified polyvinyl acetal resin has a flow softening point of 100° C. to 150° C., and a coating paste including the same.
However, even in the paste described in Patent Document 1 or 2, because of the presence of the composite resin including the (meth)acrylate monomer and polyvinyl acetal or the modified polyvinyl acetal resin, adhesion is low compared with the case of a simple acrylic resin whose glass transition point (Tg) can be controlled to a relatively low level. Furthermore, the resin described in Patent Document 1 is soluble only in a solvent that is likely to swell or dissolve polyvinyl butyral contained in ceramic green sheets and the like, and therefore, the resin is likely to damage ceramic green sheets.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2005-15654
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2006-210256